Ammonia evolved from 0.75 g of the soil sample in the Kjeldahl’s method for nitrogen estimation, neutralises 10 ml of 1M H2SO4. Find the percentage of nitrogen present in the soil

The correct option is 37.33.

Here is the step-by-step explanation of the solution based on Kjeldahl's method for nitrogen estimation:

1. Understand the chemical reactions involved:
In Kjeldahl's method, nitrogen in the organic sample (soil) is converted to ammonia (${\mathrm{NH}}_3$). The evolved ammonia is then neutralised by a standard acid, in this case, sulfuric acid ($H_2{\mathrm{SO}}_4$).
The balanced neutralization reaction between ammonia and sulfuric acid is:
$2{\mathrm{NH}}_3+H_2{\mathrm{SO}}_4\to {\left({\mathrm{NH}}_4\right)}_2$
From this stoichiometry, 1 mole of $H_2{\mathrm{SO}}_4$ neutralises 2 moles of ${\mathrm{NH}}_3$. Since 1 mole of ${\mathrm{NH}}_3$ contains 1 mole of nitrogen atoms (N), 1 mole of $H_2{\mathrm{SO}}_4$ is equivalent to 2 moles of nitrogen atoms.

2. Calculate the moles of acid used:
We are given:
Volume of $H_2{\mathrm{SO}}_4$ solution = 10 ml = 10 × 10^-3 L
Molarity of $H_2{\mathrm{SO}}_4$ solution = 1 M
Moles of $H_2{\mathrm{SO}}_4$ = Molarity × Volume (in L)
$\text{Moles of}{H}_2{\mathrm{SO}}_4=1\times 10\times {10}^{-3}=0.01\text{mol}$

3. Determine the moles and mass of nitrogen:
Since 1 mole of $H_2{\mathrm{SO}}_4$ neutralises 2 moles of nitrogen (N):
$\text{Moles of nitrogen}=2\times \text{Moles of}{H}_2{\mathrm{SO}}_4=2\times 0.01=0.02\text{mol}$
Now, find the mass of this nitrogen using the molar mass of nitrogen (14 g/mol):
$\text{Mass of nitrogen}=\text{moles}\times \text{molar mass}=0.02\times 14=0.28\text{g}$

4. Calculate the percentage of nitrogen in the soil sample:
The total mass of the soil sample is 0.75 g.
The percentage of nitrogen is calculated as:
$\text{Percentage of Nitrogen}=\frac{\text{Mass of Nitrogen}}{\text{Total mass of sample}}\times 100$
$\text{Percentage of Nitrogen}=\frac{0.28}{0.75}\times 100=37.33\%$
Therefore, the percentage of nitrogen present in the soil is 37.33%.